Treatment of rosin



Patented Apr. 20, 1948 UNITED STATES PATENT OFFICE- 2.439.807 TREATMENT OF ROSIN Arthur W. Hixson, ler, New York, N. Foundation,

Delaware, as trustee No Drawing. Application Leonia, N. Y., assignors to The Chemical Incorporated, a corporation of 1., and Ralph Mil- May 14, 1941,

Serial No. 393,481 16 Claims. (Cl. 260-108) third source of rosin is tall oil, which comprises a mixture of rosin acids, fatty acids and nonsaponifiable material.

Generically considered, rosin consists essentially of a are definite diiferences in thegum and wood rosins which are evident in certain chemical and physical constants. The wood rosin is of a low grade on the rosin scale and is characterized by found in gum rosins. Since for many applications is intreated to decrease its color.

There are several methods of refining rosin which have been utilized. One of these consists in dissolving the rosin in a low boiling petroleum low boiling naphtha. The naphtha solution is then treated with a selective solvent, such as furfural which has a greater affinity for the color bodies than rosin. Another this field it has been found that by a method that is as in which, so to speak, the whole rosin content was attempted to be segregated from the color bodies. It is thus possible, under the present invention, to produce rosin fractions lighter than rade X if desired.

The present invention is based upon the discovery of unique and unexpectable efiects which obtain in a liquefied, normally gaseous hydrocarrosin and some of the mally present in rosin. Attempts have been made in the past to utilize this fact to separate color bodies from rosin but only to the extent that the color bodies are relatively insoluble and the rosin is relatively soluble in the solvent. This is tosay that prior to the present discovery the decolorlzing of rosin by means of solvents, such as propane, was predicated upon the assumption that rosin was substantially completely soluble in the solvent. It has been discovered, however. contrary to prior postulates, that when solutions of rosin in liquefied, normally gaseous hydrocar bons are warmed some of the material comes out of solution in a lower immiscible second liquid phase. It has been discovered further that the solubility of the color bodies which are dissolved. in the stated solvents decreased much more rapidly than the solubility of the rosin acids. The present process is based upon these two hitherto unknown facts and in a word comprise the refining and fractionation of crude rosin by dissolution in a liquefied, normally gaseous hydrocarbon and then the controlled insolubilizing of predetermined constituents by a thermal control of the system. I

In actual mechanism the process consists in dissolving the rosin to be clarified and/or fractionated in a liquefied, normally gaseous hydrocarbon, such as propane, warming the resultant solution to effect the precipitation of certain constituents lower immiscible second liquid phase, then septhe original lower precipitated phase is darker than the inal rosin.

orig- By repetition of this treatment,

* 'ployed.

. secured and the tional sense or removing color bodies) but also to iractionate it. The process or fractionation may be continued to any desired degree by the method described. namely by continuously retreating the phase consistin oi the rosin dissolved in the solvent by the simple expedient or elevating the temperature and eilecting the formation of a second phase containing materials precipitated or insolubilized by elevation of the temperature. It has been found in actual practice that after the second sizable rosin phase, 1. e. the second precipitated phase. has been removed iew ii any color bodies will be dissolved in the liquefied, normally gaseous hydrocarbon.

In carrying out the invention propane is the preferred liquefied, nuormally gaseous hydrocarbon although it is clearly to be understood that other liquefied, normally gaseous hydrocarbons or mixtures thereof can be utilized. When other such liquefied, normally gaseous hydrocarbons or mixtures thereof are employed it will be understood that the particular temperature employed for phase formation will be varied correspondingly. The advantage of propane over the other saturated, liquefied, normally gaseous hydrocarbons resides in the fact that the entire process can be carried out readily in the approximate temperature range C. to 100 C. Propane also presents the advantage of being able to dissolve a substantial quantity of rosin without dissolving a large amount or color bodies. Ethane has only a small dissolving capacity for rosin so that if this is used alone very large quantities of ethane must be circulated per pound of resin refined. Butane and isobutane dissolves rosin in adequate amounts but they also more readily dissolve the color bodies than does propane. A mixture of ethane and butane, for example, can be used to substantially duplicate the results obtained with propane.

As will be appreciated by those skilled in the art; the ratio of solvent to rosin which is utilized will depend upon the particular solvent em- When propane is used, rrom to parts of solvents to 1 part of rosin, by weight. is suitable. As will have been appreciated, the temperature to which solvent is heated will depend upon the quality of the rosin that is desired. In a typical example, i. e. using propane as the solvent and "N" grade gum rosin, a temperature of about 70 C. will insure the production oi a rosin fraction having a color which will grade about 2: and probably higher. In accordance with the invention, by operating at the higher temperatures lighter colored rosin products may be higher the temperature to which the solution is warmed the lighter will be the color oi the product recovered with. naturally, a decrease in the yield.

It will be appreciated that the present process is essentially a thermal separation process operating in a solvent medium. In these circumstances, it is apparent that the lower phase may be retreated to secure a greater yield oi light colored rosin, that is to say, the lower phase. after separation, may be refractionated in accordance with the principles or the invention. The process may be conducted as a batch process or preferably it may be eflected in a continuous counter-current extraction system.

The present process presents potentialities not inherent in earlier methods. For example, rosin is frequently employed under conditions where it is advantageous to have it in finely divided term. Such finely divided form may readily be 4 secured in the present method. I! the liquefied,

normally gaseous hydrocarbon containing the dissolved rosin is discharged into a chamber maintained at about atmospheric pressure and at a temperature above the normal boiling point of the solvent, the solvent rapidly volatilizes and rosin in the form of small frangible fragments is produced. The volatilization oi the solvent refrigerates the solid phase rosin so that its tendency to melt and adhere to contiguous particles is greatly diminished. The solid particles thus produced may be subjected to a vacuum to remove some oi the occluded gas. Rosin formed in this manner is very white in color. presents a fractions from resins large bulk for a given weight and is very reactive, dissolving in the rosin solvents very rapidly. Such a method presents marked advantages over earlier attempts to produce rosin in small particle phase. Such earlier attempts comprise an ordinary grinding operation but the frictional heats generated during grinding make the rosin particles sticky. In order to obviate this diillculty rosin has been ground in the presence oi about 10% of bentonite. While this method does improve the grinding operation it eventuates in a product which contains an inert diluent. As compared to such prior methods the improved method of producing the rosin in finely divided form presents marked advantages.

It will be seen that the process of producing and refining rosin described herein represents a real advance. By utilization or the process, improved grades oi rosin characterized by an extremely light color are obtainable. The process. as pointed out, presents the decided advantage of being operable upon different types oi rosin source material to produce uniform or standardized grades of rosin or improved properties.

While preferred embodiment of the invention has been described it is to be understood that this is given to exemplify the underlying principles involved and not as limiting the useful scope of the invention to the particular treatments described.

We claim:

1. The process of securing a plurality of rosin having fractions insoluble in liquefied hydrocarbons from a solution of rosins dissolved in liquefied, normally gaseous raflln hydrocarbons comprising warming the solution until a rosin phase appears, separating the rosin phase from the hydrocarbon phase, raising the temperature of the hydrocarbon phase until a second rosin phase appears, separating the second rosin phase from the hydrocarbon phase and repeating the cycle until substantially all the rosin has been separated from the hydrocarbon phase.

2. The process of refining rosin which comprises dissolving the rosin in a liquefied, normally gaseous parailln hydrocarbon. heating the solution to predetermined states of elevated temperatures at which rosin fractions precipitate from the solution to form a separate rosin phase and removing from the solution the several rosin phases which form respectively at the said temperature stages.

3. The process of refining rosin which comprises dissolvlng rosin in liquefied propane, heating the propane solution to predetermined stages of elevated temperature at which rosin fractions precipitate from the propane solution, as a separate liquid phase removing from the solution the separate rosin phases which form respectively at said temperature stages.

effect a precipitation comprises dissolving rosin,

4. The process of refining rosin which comprises dissolving rosin in liquefied propane, raising the temperature to approximately 70 C. to

uents of the rosin insoluble in the propane at such temperature, separating the precipitated material, warming the solution to a higher temperature to eiTect precipitation of additional constituents insoluble in the propane at such higher temperature, separating such constituents and recovering the residual rosin constituents from the remaining solution.

5. The process of refining gum rosin which comprises dissolving the rosin in a liquefied, normally gaseous parafiin hydrocarbon, heating the solution to predetermined states of elevated temperatures at which difierent rosin fractions are precipitated. as substantially immiscible liquid phases and removing from the solution the several rosin phases which form respectively at the said temperature stages.

6. The process of refining wood rosin which comprises dissolving the rosin in a liquefied, nor mally gaseous parafrln hydrocarbon, heating the solution to predetermined states of elevated temperatures at which different rosin fractions are precipitated as substantially immiscible liquid of predetermined constiting the lower phase to further fractionate its contained rosin constituents.

' 12. In the refining of rosin that improvement which comprises dissolving the rosin, which contains color bodies, in a liquefied normally gaseous hydrocarbon solvent of the type in which the rosin and naturally occurring associated color bodies are more soluble at lower than at higher temperatures of the solvent and in which the solubility of the color bodies decreases more rapidly than the solubility of the rosin with elevation of temperature of the solvent, then raising the temperature of the system to that predetermined dephases and removing from the solution the several rosin phases which temperature stages.

7. The process of refining tall oil rosin which comprises dissolving the rosin in a liquefied, normally gaseous paraifin hydrocarbon, heating the solution to predetermined states of elevated temperatures at which rosin fractions are precipitated as substantially immiscible liquid phases and removing from the solution the several rosinphases which form respectively at the said temperature stages.

8. A method of producing refined rosin which which contains color bodies, in liquid propane in the ratio of approximately 1 part of rosin to from 10 to 15 parts of propane, raising the temperature to substantially 70 C. to efiect the formation of a second lower liquid phase containing color bodies and some rosin, removing the solvent phase containing dissolved constituents of rosin and recovering such constituents from the solvent.

9. A method of refining rosin which comprises dissolving rosin, which contains color bodies, in a liquefied, normally gaseous paraffin hydrocarbon and elevating the temperature to a degree sufficient to form a second liquid phase containing undesired color constituents and some rosin, separating such second liquid phase and recovering the residual rosin constituents from the hydrocarbon solution.

10. A method of refining rosin which comprises dissolving rosin in liquid propane, elevating the temperature to a point above 70 (2., separating a lower liquid phase which forms at such temperature and recovering a clarified remaining solution.

11. A method of refining rosin which comprises dissolving rosin, which contains color bodies, in a liquefied, normally gaseous parafiln hydrocarbon, heating the solution to a. temperature above the maximum solubility temperature for color bodies and certain rosin constituents and to insure the form respectively at the said formation of a separate lower liquid phase containing insolubilized constituents of the rosin, separating the phases thus, formed, recovering a clarified rosin fromthe upper phase, and treatrosin from the.

gree at which the desired decolorizing action is achieved as represented by the insolubilizing of the color bodies and some rosin and then accumulating such color bodies in a lower stratifiedliquid phase while a substantial proportion of the rosin is retained in solution in the stratified upper phase, then separating such lower phase and recovering a rosin fraction of predetermined color characteristics from the upper solvent phase.

13. A process according to claim 12 in which the separated lower phase is redissolved in the said solvent with subsequent elevation of the temperature of the solvent to further fractionate the contained rosin-like constituents;

14. A process in accordance with claim 12 in which the upper phase is further elevated in temperature to further fractionate its contained rosin-like constituents by selective thermal insolubiliziation in the same liquid system.

15. The process of refining rosin which comprises dissolving rosln, which contains color bodies, in liquefied propane in a continuous countercurrent extraction system, heating the propane solution in the system to a temperature at which two liquid phases are formed the temperature being such that the color bodies and a minor fraction of the rosin are insolubilized and accumulate in the lower liquid phase, continuously separating the two liquid phases and recovering the solvent associated with each phase.

16. The process of refining rosin which comprises dissolving rosin, which contains color bodies, in a liquefied normally gaseous parafiin hydrocarbon in a continuous countercurrent extraction system, heating the hydrocarbon solution in the system to a temperature at which two liquid phases are formed the temperature being such that the color bodies and a minor fraction of the rosin are insolubilized and accumulate in the lower liquid phase, continuously separating the two liquid phases and recovering the solvent associated with each phase.

ARTHUR W. HIXSON. RALPH MILLER.

REFERENCES CITED The following-references are of record in the file of this patent:

UNITED STATES PATENTS neers (London), vol. 9 (1930), pages 40 to 45. 

